Brushless motor with balance ring diode

Abstract

The invention relates to a brushless motor with balance ring diodes. The brushless motor comprises a housing, a stator assembly, a rotor assembly, a rotary transformer and a rectifier. The stator assembly is disposed within the housing and includes a stator winding disposed on a stator core. A rotor assembly is also positioned within the housing with an air gap separating the rotor assembly from the stator assembly. The rotor assembly includes a rotor shaft, a rotor winding, and a balance ring. A resolver is positioned within the housing and includes a primary coil and a secondary coil. The rectifier includes a plurality of diodes positioned on a balance ring. A rectifier is electrically connected between the secondary coil and the rotor winding.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 588,975, filed on October 9, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the field of electric machines, and more particularly to propulsion motors for electric vehicles. Background Art

[0004] In modern electric vehicle engine compartments, space is limited and there is often a need to reduce the packaging size of the electric motor and other components in order to allow all of the parts to fit within the engine compartment. Additionally, it is desirable to limit the number of parts required in the vehicle while still meeting the electric motor and other vehicle operating requirements. There is also a need to properly cool the motor components, including diodes, coil windings, and other related parts, in order to maintain the performance of the motor and keep it in good working condition.

[0005] Electrically excited synchronous motors ("EESMs") are well known and can be found in a variety of applications, including motors for electric vehicles. EESMs have the advantages of being high efficiency motors that are relatively inexpensive to manufacture, can be safely operated, and have efficient field weakened operation. EESMs can be provided as brushed electrically excited synchronous motors (i.e., "brushed EESMs") or induction electrically excited synchronous motors (i.e., "brushless EESMs").

[0006] An example of a brushed EESM is Fig. 10A . The rotor 130 of the brushed EESM defines a north / south pole provided in the form of a coil wound on a core. The slip rings 114 transfer energy to the rotor coils via brushes 116 that contact the slip rings. Unfortunately, the physical engagement between the brushes 116 and the slip rings 114 causes significant wear over time and reduces the life of the brushed EESM. The slip rings 114 and brushes 116 must also be isolated from the oil spray intended to cool and lubricate the motor parts, thereby creating additional parts in the motor. In addition, the slip rings 114, brushes 116 and related components consume a large amount of axial space in the EESM.

[0007] Brushless EESM does not require slip rings and brushes. In a brushless EESM, current is induced in the rotor coil via a rotary transformer. The rotary transformer includes a fixed primary coil and a movable / rotating secondary coil. The provided rotating secondary coil is attached to the rotor shaft and rotates with the rotor shaft. The fixed primary coil is adjacent to the rotating coil, but is fixed relative to the housing. When the fixed primary coil is energized and the secondary coil rotates, current is induced in the secondary coil. The current from the rotating secondary coil is then transferred to the rotor coil. However, the current induced in the secondary coil is alternating current ("AC"), and the current flowing through the rotor coil needs to be direct current ("DC"). Therefore, a rectifier and associated electronic device packaging are required to convert the current from AC to DC. Advantageously, the brushless EESM does not include brushes or other physical connections to transfer current to the rotor coil. In addition, the axial length of the rotary transformer and electronic device packaging in the brushless EESM is significantly smaller than the slip rings and brushes of the brushed EESM, thereby reducing the axial length of the motor.

[0008] While a brushless EESM provides inherent advantages over a brushed EESM, it would be an additional advantage to improve upon current brushless EESM designs. For example, it would be advantageous to provide a brushless EESM with an axial length that is further reduced from existing designs. It would also be advantageous to provide improved cooling and heat transfer for the electronics packaging of the brushless EESM. In connection therewith, it would be advantageous to provide an EESM that provides these advantages with only a limited number of parts, thereby reducing the complexity and manufacturing cost of the motor. Summary of the invention

[0009] A brushless motor is disclosed herein. In at least one embodiment, the motor includes a housing, a stator assembly, a rotor assembly, a rotary transformer, and a rectifier. The stator assembly is arranged in the housing and includes a stator winding disposed on a stator core. The rotor assembly is also positioned in the housing, wherein an air gap separates the rotor assembly from the stator assembly. The rotor assembly includes a rotor shaft, a rotor winding, and a balancing ring. The rotary transformer is also positioned in the housing and includes a primary coil and a secondary coil. The rectifier includes a plurality of diodes positioned on the balancing ring. The rectifier is electrically connected between the secondary coil and the rotor winding.

[0010] In at least one embodiment, the electric machine includes a rotor assembly positioned within the housing, the rotor assembly including a rotor shaft, a rotor core, and a two-component balancing ring, the two-component balancing ring including a first component electrically isolated from a second component. The electric machine also includes a rotary transformer positioned within the housing, the rotary transformer including a primary coil and a secondary coil, the secondary coil positioned on the printed circuit board.

[0011] In at least one embodiment, the rotor assembly includes a rotor shaft, a rotor core, a rotor winding, a balancing ring, and a plurality of diodes. The rotor core is positioned on the rotor shaft, and the rotor winding is wound on the rotor core. The balancing ring is positioned at one end of the rotor core, and the plurality of diodes are positioned on the balancing ring.

[0012] The above features and advantages and other features and advantages will become more apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings. Although it is desirable to provide a brushless motor that provides one or more of these or other advantageous features that may be apparent to those reading this disclosure, the teachings disclosed herein extend to those embodiments that fall within the scope of the appended claims, regardless of whether they include or achieve one or more of the advantages or features mentioned herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 shows a cross-sectional side view of an improved brushless electric motor including a rotary transformer having a secondary coil disposed on a printed circuit board, the electric motor also including a rectifier diode disposed on a balance ring of a rotor assembly;

[0014] Figure 2 Shows Figure 1 A separated cross-sectional view of a rotary transformer and a rotor assembly;

[0015] Figure 3 Shows Figure 2 An enlarged view of the dotted line isolation block III;

[0016] Figure 4 Shown for Figure 1 A block diagram of components in an electronics package of a rotor assembly;

[0017] Figure 5 Shown for Figure 1 A perspective view of a two-piece balancing ring of a rotor assembly, the balancing ring being shown separated from a press-fit diode;

[0018] Fig. 6A Shows Figure 5 A side-by-side implementation of a balancing ring;

[0019] Figure 6B Shows Figure 5 A stacking implementation of the balancing ring;

[0020] Figure 7 is used for Figure 1 A simple schematic diagram of a rotary transformer, a rectifier arrangement with associated heat sink and an excitation winding of a motor;

[0021] Figure 8 Shows Figure 1A perspective view of a rotor assembly comprising a first balancing ring and a second balancing ring having a diode and an interpolar plastic support arranged on the rotor;

[0022] Fig. 9 yes Figure 8 a cutaway perspective view of a rotor assembly showing the location of an oil cooling path;

[0023] Fig. 10A is a cross-sectional side view of a prior art brushed EESM, wherein the square outline indicates the volume required for the brushed EESM;

[0024] Fig. 10B yes Figure 1 A cross-sectional side view of the brushless EESM, where Fig. 10A A square profile is applied on the brushless EESM to illustrate the reduced axial direction of the brushless EESM. DETAILED DESCRIPTION

[0025] This article discloses a brushless motor. Figure 1 As shown, the electric machine 10 includes a stator assembly 20 and a rotor assembly 30 disposed within a housing 12. The electric machine 10 also includes a rotary transformer 50, which includes a primary coil 52 and a secondary coil 54. The primary coil 52 is fixed relative to the housing 12 of the electric machine 10. The secondary coil 54 is disposed on a printed circuit board 56 and is configured to rotate within the housing 12 with the rotor assembly 30. The rotor assembly 30 also includes a rectifier 74, which includes a plurality of diodes 76. The rectifier diodes 76 are disposed on a balance ring 80 of the rotor assembly, which is further described in detail herein.

[0026] Continue to refer to Figure 1 The housing 12 of the electric machine is constructed of steel or other hardened metallic material and is configured to hold both the stator assembly 20 and the rotor assembly 30. The housing 12 is particularly suitable for placement in an engine compartment of a vehicle, such as an electric motor compartment of an electric vehicle.

[0027] The stator assembly 20 (also referred to herein as a "stator") is fixedly fixed in the housing 12. The stator assembly 20 includes a magnetically permeable stator core 22 and a plurality of stator windings 24 arranged in slots on the stator core. The stator windings 24 are powered by a vehicle battery 60 (not in the vehicle). Figure 1 shown in; see Figure 7 The stator electronics package includes an inverter that converts the DC voltage from the vehicle battery into an AC voltage and causes AC current to flow through the stator windings.

[0028] Now refer to Figure 1 and Figure 2The rotor assembly 30 (also referred to herein as the "rotor") is rotatably accommodated in the housing 12. The rotor assembly 30 includes a rotor shaft 32 that extends through the housing and the stator 20 and defines the axial direction of the motor 10. The rotor shaft 32 is supported by bearings 34 in the housing 12. The rotor shaft 32 is made of steel or other metal materials, and in some embodiments may be hollow (such as Figure 2 2 (shown), or may be solid in other embodiments. The rotor core 36 is coupled to the rotor shaft 32. The rotor core 36 is separated from the stator core 22 by an air gap 28. The rotor core 36 is constructed of a magnetically permeable material and defines a plurality of rotor poles. Each rotor pole holds one of a plurality of rotor coils 38 that surround the pole (the rotor coils may also be referred to as rotor windings, rotor field coils, or field coils). Balancing rings 40, 80 are positioned at opposite ends of the rotor core 36. The balancing rings 40, 80 are used to balance the rotor assembly 30 within the housing 12 so that movement of the rotor 30 does not destabilize the motor 10 during operation. The balancing rings are actively used to balance the rotor. After the rotor is completed, the rotor imbalance is measured, and then the balancing machine adds material, or subtracts material (more often subtracts) from the two balancing rings to bring the rotor below the balance specification.

[0029] like Figure 2 and Figure 3 As best shown, the rotary transformer 50 is positioned at one end of the rotor shaft 32. The rotary transformer 50 includes a primary coil 52 and a secondary coil 54 disposed within a transformer housing 58. The primary coil 52 of the rotary transformer 50 is securely fixed within the housing 12. The primary coil 52 surrounds the rotor shaft 32, but is not engaged with the rotor shaft 32 and does not move with the rotor assembly 30. Similar to the stator windings, the primary coil 52 is configured to be powered by an electronics package coupled to a vehicle battery. As explained in further detail below, the electronics package converts the DC energy provided by the vehicle battery into AC that flows through the primary coil 52 of the rotary transformer 50.

[0030] The secondary coil 54 is positioned directly opposite the primary coil 52 in the rotary transformer, with only a small air gap between the two coils 52, 54. The secondary coil 54 is arranged on a printed circuit board (PCB) 56, which is fixedly coupled to the rotor shaft 32 and extends radially outward from the rotor shaft 32. Therefore, the secondary coil 54 is configured to rotate within the transformer housing 58, and is also configured to rotate with the rotor assembly 30 within the motor housing 12. As explained in further detail below, the electronics package converts the AC current induced in the secondary coil into a DC current that is delivered to the rotor coil 38.

[0031] Now refer to Figure 4, a block diagram of the electronic components of the electronic device package associated with the rotary transformer 50 is shown. The electronic components coupled to the rotary transformer 50 include a vehicle battery 60 connected to a primary side package 62 and a secondary side package 72. The primary side package 62 includes an inverter 64 and a resonant compensation circuit 66. The secondary side package 72 includes a rectifier 74. The vehicle battery 60 can be any of a variety of vehicle batteries used to power an electric vehicle, such as a lithium-ion (Li-ion) battery (including Li-NMC, LFP, Li-NCA, etc.), a nickel metal hybrid battery, or a lead-acid battery. The vehicle battery 60 is designed for a high power-to-weight ratio and energy density.

[0032] exist Figure 4 In an embodiment of the invention, the vehicle battery 60 is an 800V battery that provides DC power to the inverter 64. The inverter 64 receives the DC current from the battery 60 and converts it into AC current. The AC current from the inverter 64 passes through the resonant compensation circuit 66, which helps to optimize power transfer, reduce energy losses and improve efficiency. The AC current is then delivered to the primary coil of the rotary transformer 50. The rotary transformer 50 induces an AC current in the secondary coil 54 of the rotary transformer. The AC current is then delivered to the rectifier 74, which converts the AC current into a DC current. The DC current from the rectifier is then delivered to the rotor excitation winding 38.

[0033] Refer again Figure 1 and Figure 2 , the brushless EESM 10 also includes two balancing rings 40, 80 positioned at opposite ends of the rotor core 36. The balancing rings 40, 80 are typically constructed of a non-magnetic material such as stainless steel or aluminum, and have strategically removed material to enable the rotor to meet maximum unbalance specifications. To reduce the number of parts in the motor 10, one balancing ring also serves as a heat sink for at least one diode of the rectifier 74. In particular, in the embodiments disclosed herein, the balancing ring 80 positioned closest to the rotary transformer 50 also serves as a diode heat sink.

[0034] Now refer to Figure 5 and Fig. 6A , the balance ring 80 is divided into two electrically isolated parts, including a first part 82 and a second part 84. As used herein, the term "electrically isolated" means that there is sufficient electrical insulation between the two parts so that current does not flow between the two parts during normal operation of the motor. The electrical isolation can be provided by a simple air gap 83 that provides sufficient spacing to insulate the first part 82 from the second part 84 to prevent, or it can be provided by a polymer or other insulating material (not shown) positioned between the first part 82 and the second part 84. Figure 5 and Fig. 6AIn the embodiment, the balancing ring 80 is divided into two halves such that the first component 82 and the second component 84 are side by side (ie, two different radially extending sides are arranged at a common axial position) and are symmetrical in shape.

[0035] When the balancing ring 80 is viewed as a whole (i.e., the first component 82 and the second component 84 positioned side by side), it will be appreciated that the balancing ring 80 includes an outer diameter wheel portion 86 and an inner diameter ring portion 92, wherein the inner diameter ring portion 92 is coaxial with the outer diameter wheel portion 86 and axially elevated relative to the outer diameter wheel portion 86. The outer diameter wheel portion 86 includes a radially extending surface 88 and an outer cylindrical surface 90. The radially extending surface 88 is plate-like and disc-shaped, and the outer cylindrical surface 90 extends axially from the peripheral edge of the radially extending surface 88 with a similar thickness. In other words, the outer cylindrical surface 90 is a circumferential surface that is substantially perpendicular to the radially extending surface 88. The radially extending surface 88 and the outer cylindrical surface 90 together form a cap-like (or cup-like) structure that is relatively thin and is configured to fit on one end of the rotor core 36.

[0036] The inner diameter ring portion 92 of the balancing ring 80 extends radially inward and axially outward from the inner periphery of the outer diameter wheel portion 86. The thickness of the balancing ring 80 at the inner diameter ring portion 92 is significantly greater than the thickness at the radially extending surface 88. A plurality of diode holes 94 are formed in the face of the inner diameter ring portion. Each diode hole 94 has a cross-sectional shape similar to the body of the diode 76 used to form the rectifier 74 (which is generally circular in shape) and has a depth sufficient to fully receive the body of the diode 76. Returning again to Figure 3 , it will be appreciated that the depth of each diode hole 94 is greater than the thickness of the radially extending surface 88 of the gimbal ring 80. Therefore, it will be appreciated that the inner diameter ring portion 92 is used to provide a portion of the gimbal ring 80 with sufficient thickness to receive the diodes 76. Advantageously, the diodes 76 are fully embedded in the diode holes 94 in the inner diameter ring 92, and the outer diameter wheel portion 86 and the inner diameter ring 92 together serve as a heat sink for each diode 76.

[0037] To mount the diodes 76 in the diode holes 94, the diodes 76 are press fit into the diode holes 94 with the entire body 78 of each diode fully received within the depth of the diode holes 94 and the leads 79 of the diode extending axially out of the diode holes 94. The leads 79 are all connected to the printed circuit board 56 of the rotary transformer 50, which is positioned adjacent to the gimbal 80. A mechanical connection such as welding, soldering, or adhesive may be used to further secure the leads of each diode to the PCB 56 (or routing to the PCB).

[0038] During operation of the motor, the diode 76 generates heat, and each of the first and second parts 82 and 84 of the gimbal 80 acts as a heat sink to dissipate heat from the diode 76 disposed in the diode hole 94. Figure 5 and Fig. 6A In the embodiment, the two heat sinks (ie, components 82 and 84 ) are side by side, so each heat sink includes 1 / 2 of the balancing ring 40 .

[0039] exist Fig. 6A In the embodiment of FIG. 8 , each component 82 , 84 of the balancing ring 80 includes at least two diode holes 94 , and the diodes 76 are connected together to form the rectifier 74 . Figure 7 A schematic arrangement of the rectifier 74 is shown, as well as the placement of a diode 76 associated with each of the two heat sinks 82, 84 (ie, provided by the first and second parts 82, 84 of the balancing ring 80). Figure 7 As shown, two diodes 76a and 76b of the rectifier 74 are arranged on "heat sink 1" (i.e., the first part 82 of the balancing ring 80), and two diodes 76c and 76d of the rectifier 74 are arranged on "heat sink 2" (i.e., the second part 84 of the balancing ring 80). One end of the rotor excitation coil 38 (i.e., the first lead to the excitation coil) is connected to the surface of one heat sink (i.e., the first part 82), and the opposite end of the rotor excitation coil 38 (i.e., the second lead to the excitation coil) is connected to the surface of the other heat sink (i.e., the second part 84). Each connection to the heat sink is a mechanical connection, such as welding or brazing for fixing the end of the rotor excitation coil 38 to the heat sink.

[0040] The rotary transformer 50 and the rectifier 74 are used together to deliver DC current to the excitation winding 38. In operation, AC current is provided to the primary coil 52 of the rotary transformer 50 from the vehicle battery 60. The magnetic flux provides coupling between the primary coil 52 and the secondary coil 54 of the rotary transformer 50 and induces AC current in the secondary coil 54. The AC current from the secondary coil 54 of the rotary transformer 50 is then delivered to the rectifier, which converts the AC current to DC current that is delivered to the excitation winding 38 using four diodes 76a-76d mounted on the heat sink (i.e., components 82 and 84 of the balancing ring 80).

[0041] Although Figure 5 , Fig. 6A and Figure 7 One embodiment of a balancing ring 80 with a rectifier diode 76 mounted thereon is shown, but it will be appreciated that other embodiments are contemplated. For example, Figure 6BAn alternative embodiment of a gimbal 80 is shown in which a two-part gimbal 80 is provided by a first part 82 that is axially forward / rearward of a second part 84. In other words, Figure 6B In the illustrated alternative embodiment of the gimbal 80, one heat sink for the diode 76 is provided by a first component 82 that serves as the gimbal itself, and a second heat sink is provided by a second component 84 that is electrically isolated from the first component and mounted axially forward or rearward from the first component. Figure 5 and Fig. 6A The outer diameter wheel portion 86 is a unitary component of the same general shape (i.e., including the radially extending surface 88 and the cylindrical outer surface 90), but Figure 6B In the embodiment, the first component 82 is not divided into two different side-by-side components (such as Figure 5 and Fig. 6A In this embodiment, the depth of the radially extending surface 88 of the first component 82 is sufficient so that the diode hole 94 on the first component 82 completely receives the body of the diode 76 installed therein. Figure 6B As shown, the second component 84 is provided by a smaller ring disposed at a different axial position than the first component 82 (i.e., axially forward or rearward from the first component 82). Likewise, the depth of the second component 84 is sufficient so that the diode hole 94 on the second component fully receives the body of the diode mounted therein. An insulating ring 96 may be disposed between the first component 82 and the second component 84 to help electrically isolate the first component 82 from the second component 84.

[0042] In view of the foregoing, it will be appreciated that in each case of a gimbal (e.g. Fig. 6A and Figure 6B ), the heat sinks (i.e., components 82 and 84) should be electrically isolated from each other and grounded. Therefore, the method and apparatus for attaching the balancing ring 80 to the rotor assembly should result in the balancing ring being insulated from other metal parts of the rotor assembly. In some cases, the rivets or screws used to attach the balancing ring are screwed into the inter-pole insulating support 44 extending axially along the rotor core 36, such as Figure 8 As shown. The inter-pole insulating supports 44 provide electrical isolation between the rotor coils that define the poles on the rotor. The inter-pole insulating supports may be formed of plastic or any of a variety of other electrically insulating materials sufficient to provide electrical isolation between the poles. Using a plastic material for the inter-pole insulating supports 44 is advantageous because it allows metal rivets or screws to be used to attach the balancing rings 40, 80 to the rotor core 36.

[0043] It will also be appreciated from the disclosure herein that the design of the electric machine 10 is such that each of the rotary transformer 50 with the PCB 56, the rectifier 74 (including the diodes 76), and the balanced annular heat sinks 82 and 84 are located in the oil cooling cavity of the electric machine near the rotor 30 and the rotor coils 38. Fig. 9 As shown by arrows 99 in FIG. 1 , during operation of the motor, cooling oil delivered to the rotor assembly 30 is ejected from the oil holes 98 on the cylindrical surface portion 90 of the balancing rings 40, 80 via circumferential force. As a result, the rotary transformer 50 (including the PCB 56) and the rectifier diode 76 are mounted in the cooling cavity and are cooled by the oil ejected from the rotor holes on the balancing rings 40, 80.

[0044] Now refer to Fig. 10A and 10B It will be further appreciated that the axial length of the brushless EESM 10 disclosed herein is significantly less than the brushed EESM 110 of the prior art. Fig. 10A Box 118 shows the space consumed in the brushed EESM between opposite ends of the rotor shaft 132 exiting the housing 112 . Fig. 10B The same frame 118 is shown superimposed on the brushless EESM 10 disclosed herein. Fig. 10B It can be easily seen that the brushless EESM 10 occupies significantly less space in the axial direction than the prior art brushed EESM 110. In particular, Fig. 10B Section line 119 within box 118 indicates the axial space savings achieved using the brushless EESM disclosed herein.

[0045] In view of all of the foregoing, it will be appreciated that the design of the electric machine 10 in the form of a brushless EESM having a rotary transformer 50 and a press-fit diode 76 disposed on a gimbal 80 disclosed herein has many advantages. These advantages include the following:

[0046] - Reduce the length of the machine to improve packaging;

[0047] -All parts of the rotary transformer are installed in the oil cooling chamber;

[0048] - the diode is effectively cooled due to being located in a heat sink; and

[0049] -The number of parts is reduced since the secondary coil is included on the PCB and the diode is pressed into the heat sink.

[0050] Although various embodiments of brushless motors with balanced ring diodes have been provided herein, those skilled in the art will appreciate that other implementations and adjustments are possible. In addition, aspects of the various embodiments described herein may be combined with or replaced with aspects from other features to derive embodiments different from those described herein. Therefore, it should be understood that the various and other features and functions disclosed above, or their alternatives, may be desirably combined into many other different systems or applications. Those skilled in the art may subsequently make various currently unforeseen or unanticipated substitutions, modifications, changes or improvements, which are also intended to be covered by the appended claims.

Claims

1. A motor, comprising: case; a stator assembly positioned within the housing, the stator assembly including stator windings; a rotor assembly positioned within the housing, wherein an air gap separates the rotor assembly from the stator assembly, the rotor assembly comprising a rotor shaft, rotor windings, and a balancing ring; a rotary transformer positioned within the housing, the rotary transformer comprising a primary coil and a secondary coil; and A rectifier including a plurality of diodes positioned on the balancing ring is electrically connected between the secondary coil and the rotor winding. 2 . The motor according to claim 1 , wherein the secondary coil is disposed on a printed circuit board. 3 . The electric machine of claim 2 , wherein the printed circuit board is fixedly connected to the rotor shaft. 4 . The electric machine of claim 3 , wherein the balancing ring comprises a plurality of diode holes, and the plurality of diodes are arranged in the plurality of diode holes. 5 . The electric machine of claim 4 , wherein the plurality of diodes are press-fit into the plurality of diode holes.

6. The electric machine of claim 4, wherein the balancing ring provides a heat sink for the plurality of diodes.

7. The electric machine of claim 6, wherein the balancing ring comprises a first component electrically isolated from a second component.

8. The electric machine of claim 7, wherein the first component and the second component are positioned side by side at a common axial position.

9. The electric machine according to claim 8, wherein the balancing ring comprises an outer diameter wheel portion and an inner diameter ring portion, the inner diameter ring portion is coaxial with the outer diameter wheel portion and axially elevated relative to the outer diameter wheel portion, wherein the plurality of diode holes are arranged on the inner diameter ring.

10. The electric machine of claim 9, wherein the outer diameter wheel portion comprises a radially extending surface and an outer cylindrical surface.

11. The electric machine of claim 10, wherein the outer cylindrical surface includes a plurality of oil holes.

12. The electric machine of claim 7, wherein the second component is axially stacked on the first component. 13 . The electric machine of claim 7 , wherein the rotor winding includes a first end connected to the first portion of the balancing ring and a second end connected to the second portion of the balancing ring.

14. The electric machine of claim 13, wherein the connection between the first end of the rotor winding and the first component is a weld.

15. A motor, comprising: a rotor assembly positioned within the housing, the rotor assembly comprising a rotor shaft, a rotor core, and a two-component balance ring, the two-component balance ring comprising a first component electrically isolated from a second component; as well as A rotary transformer is positioned within the housing, the rotary transformer comprising a primary coil and a secondary coil, the secondary coil being positioned on a printed circuit board.

16. The electric machine of claim 15 further comprising a rectifier comprising a plurality of diodes positioned on the two-part balancing ring.

17. The electric machine of claim 15, wherein the dual component balancing ring includes a first component and a second component electrically isolated from the first component.

18. A rotor assembly comprising: Rotor shaft; a rotor core positioned on the rotor shaft; a rotor winding wound on the rotor core; a balancing ring positioned at one end of the rotor core; as well as A plurality of diodes are positioned on the balancing ring.

19. The rotor assembly of claim 18, wherein the plurality of diodes are connected to form a rectifier, the rectifier is connected to the rotor winding, and the balancing ring comprises: first component; a second component electrically isolated from the first component; as well as A plurality of diodes are positioned on the first component and the second component.

20. The rotor assembly of claim 19, wherein the plurality of diodes are press fit into diode holes on the first and second parts of the balance ring.

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